| Many researches have proved that, apart from surface chemistry property and topological structure, the stiffness of extracellular matrix (ECM) has a great influence on cell adhesion, survival, proliferation and motility. While, the microenvironment of cells in vivo is dynamic and undergoes remodeling with time. The mechanical stiffness is dynamically changing according with temporal variations of ECM in the development, aging, and pathological processes. Hydrogel with tuneable stiffness is a sophisticated platform and has been employed for many studies of cell adhesion. However, there are few techniques of surface modification that could be used for control of surface stiffness. Polyelectrolyte multilayer films (PEMs), which are fabricated by layer-by-layer (LbL) assembly technology, have been recognized as a powerful tool to modify material surface with a variety of surface properties. Disulfide (S-S) bond is a reversible covalent linkage. It can be formed with the presence of relative weak oxidizing agent and reduced back to thiols under mild condition. In this study, (PLL/HA) multilayers with dynamic stiffness property were developed.Firstly, the thiol modified hyaluronan (HA-SH) was synthesized and then alternately deposited with PLL to fabricate thin multilayers. The result of QCM proved that the frequency shifts (-ΔF) and each deposited PLL/HA-SH bilayer, indicating the successful fabrication of (PLL/HA-SH) multilayers. Furthermore, the vertical section of (PLL/HA-SH)12 multilayers was observed using a confocal laser scanning microscope (CLSM):a thin and homogeneous multilayer film was clearly observed. The thickness was estimated to be 3.45 μm. The stiffness of the freshly prepared (PLL/HA-SH) multilayers was 60±7.6 KPa. After cross-linking by CaT, the value was increased to 210±31 KPa, indicating the successful formation of disulfide linkages, corresponding with UV-vis results. Subsequently, the cross-linked multilayers were treated with GSH for 4 h to conduct stiffness measurement. The stiffness was reduced to 68±16 KPa, which was close to that of the non-cross-linked multilayers.1 3T3 cell could’t adhere to the non-cross-linked films, whereas they can adhere well on the cross-linked ones. To investigate the 3T3 cells’ response to changeable stiffness, cells were incubated on the cross-linked multilayers for 4 h. After that, GSH was added to culture medium to a final concentration of 10 mM, and cells were continuously incubated for 10 h. After GSH treatment, the cells’ morphology changed significantly:from spreading to rounded shape, just like cells on the non-cross-linked multilayers and the activity of cells decreased by 30%. We can control of the morphology of 3T3 cells in situ through the change of stiffness.2 For cardiovascular implant materials, endothelial cells should achieve good adhesion and rapid proliferation. After the endothelial cells form to endodermis, it can maintain endothelial function. Many researches have proved that increasing the stiffness of surface is good for the adhesion of endothelial cells and decreasing the stiffness is helpful for maintaining the endothelial function. We cultured endothelial cells on the CaT cross-linked poly(L-lysine)/thiol modified hyaluronan (PLL/HA-SH) multilayer films to form endodermis. Then GSH was used to decrease the stiffness of multilayers. And the results proved endothelial cells on substrates with low stiffness showed better integrity and higher level of expression of endothelial nitric oxide (NO) than those on the substrates with high stiffness. It demonstrated the substrates with low stiffness could benefit promotion of endothelial function. |
PDF Full Text Request